Early tree regeneration response following adaptive silviculture treatments in northern hardwood ecosystems

Studying the regeneration phase of forests can be extremely valuable. Seedlings and saplings compete through this most vulnerable life phase for trees, but their survival has significance: trees that endure these early years will become the future forest canopy. Because regeneration outcomes today may define forest composition long into the future, forest managers should incorporate future climate conditions into their planning so they can promote species that are projected to have better outcomes under climate change. Unfortunately, there has been little research to explore how climate-adaptive management supports regeneration outcomes.

A new Forest Ecology and Management study led by NE CASC researchers Jess Wikle and Anthony D’Amato addresses this knowledge gap by examining the application of the Adaptive Silviculture for Climate Change Resistance-Reslilience-Transition (RRT) Framework at an ASCC installation in northern New Hampshire five years after management. The goal of the study was to learn how each of four approaches--resistance, resilience, transition and no action--influences regeneration composition and functional trait identity, characteristics that align with adaptability to future climate conditions.

The study found that the seedling size class, which largely established after experimental treatments were applied, showed response to the adaptive management activities while the sapling class more closely reflected impacts of historic management techniques. The treatments were moderately successful in shifting the regeneration composition toward desired future conditions described in each adaptation approach. Both the no action and resistance treatments resulted in a regeneration composition that closely matched canopy composition, while transition created the greatest divergence from the canopy, which was supported by planting of species expected to respond more favorably to climate change. The resilience approach resulted in a wide range of regeneration composition (including areas that matched canopy composition and those with considerable divergence from the canopy), which may offer a species mix best suited to absorb a broad range of climate change and disturbance-related impacts. When examined through the lens of functional traits, each treatment resulted in a slightly different suite of traits than others, with the exception of transition, which diverged significantly from the others, likely due to the influence of the planted seedlings. In summary, the adaptive treatments led to regeneration profiles that aligned well with pre-management objectives; in some cases, though, changes were small, and it is likely that future management interventions will be needed for these stands to continue on desired adaptation trajectories.